One image-forming apparatus known in the art includes a belt unit having a belt, and a drive roller that drives the belt; a coupling having a movable part configured to advance toward and couple with the drive roller and to uncouple and retract from the drive roller; a cover configured to open and close an opening formed in a main body; and an interlocking mechanism configured to advance and retract the movable part of the coupling in association with the opening and closing of the cover. In this image-forming apparatus, the movable part is configured to be retracted from the drive roller when the cover is opened and to be coupled with the drive roller when the cover is closed.
However, in this conventional mechanism, the movable part of the coupling is configured to move in association with the opening and closing of the cover. Since the cover is frequently opened and closed when resolving paper jams, replacing toner cartridges, and the like, the movable part is frequently uncoupled from and coupled to the drive roller, even in cases when the belt unit is not being removed or mounted. Consequently, coupling portions of the movable part and the drive roller may become worn.
Further, since the movable part of the coupling is configured to move in association with the movement of the cover, the connection provided by the coupling may become unstable when the cover is not completely closed.